The invention relates to improvements in lamps, especially sunlamps, which emit radiation in the visible and ultraviolet ranges of the spectrum.
It is already known to fill the envelope of a sunlamp with a mixture of radiation emitting substances which ensure that the lamp can emit radiation in the visible as well as in the UVA band of the ultraviolet range of the spectrum. The effect of such lamps strongly resembles that of sunlight except that the lamps cannot radiate the same amount of heat energy. However, the addition of a substance which causes the lamp to radiate in the UVA band affects a pronounced reduction of radiation in the visible range, i.e., the brightness of such lamps is less than satisfactory.
It is also known to confine in the envelope of a lamp a substance which has pronounced radiation peaks in the red, blue and green portions of the visible range, i.e., in those portions of the visible range in which the human eye is particularly sensitive so that the lamp can be categorized as a "bright" lamp.